Treatment of textile materials with radiation and caustic alkali



United States Patent 3 502 426 TREATMENT OF TExTiLE MATERIALS WITHRADIATION AND CAUSTIC ALKALI Hans Kriissig, Fritz Miinzel, andHans-Joerg Schenkel,

Schwerzenbach, Switzerland, assignors to Heberlein Patent Corporation,New York, N.Y., a corporation of New York Filed Mar. 3, 1965, Ser. No.436,810 Claims priority, application Switzerland, Mar. 13, 1964,3,272/64 Int. Cl. D06m N00 US. Cl. 8-116 8 Claims This invention relatesto the treatment of fabrics, and more particularly, it relates to aprocess for the removal of radiation energy from irradiated cellulosictextile materials.

For purposes of this application the terms textile material or fabricshall both be understood to include fabrics and textile materials of allkinds, including fibers, yarns, threads, and any manner of knit or wovenfabrics, as well as non-Woven or felted fabrics. Further, for purposesof this application the term cellulosic textile material shall beunderstood to include fabrics of all kinds which consist entirely ofnatural and/ or regenerated cellulose and mixtures thereof as Well asall manner of fabrics, films, or sheets in which such cellulosicconstituents make up a significant portion thereof.

A number of processes to improve the wearing qualities of cellulosicfabrics by subjecting such fabrics of ionizing radiation are known inthe art. Thus, cellulosic textile materials have been subjected toelectromagnetic radiation, such as gamma rays emanating fromradio-isotopes such as C0 or Cs X-rays, ultraviolet rays, and the likeor by the use of particulates ionizing radiation such as electronsaccelerated in cascade, Van de Graaf, and linear accelerators and thelike or by Tesla transformers. Such irradiation of fabrics is believedto produce ions, ion radicals, free radicals, or activated molecules orgroups of molecules which are capable of forming sites for crosslinkingbetween atoms comprising the molecule, as disclosed in copendingapplication Ser. No. 111,900. Such irradiation also fosters graftingreactions, especially in the case of monomeric substances which arecapable of being polymerized or the graftable polymers disclosed incopending application Ser. No. 125,088.

Such irradiation of textile materials results in the accumulation ofabsorbed radiation energy in the fabric. While some of this energy isconsumed in cross-linking and grafting reactions, the absorbed radiationenergy is not and apparently cannot be completely utilized, probablybecause some of it is localized in areas of the structure, such ascrystalline areas, which are inaccessible to the grafting chemicals orbecause some of the absorbed energy is present in a form which is notsuitable for grafting or cross-linking reactions between the molecules.This energy which is present in the irradiated textile material andwhich cannot be utilized for cross-linking or grafting is designatedherein as residual energy.

The residual energy remaining in the material may be very persistent andenduring. Some of the areas which have been activated by irradiation mayhave a long life and the textile material may retain the residual energyfor a long time. Moreover, this residual or stored energy does notremain quiescent or inactive in the material, but in many cases iteffects gradual changes in the physical properties, mechanical strength,and so on of the material.

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Naturally, such subsequent changes in the properties of the treatedirradiated fabric are undesirable. Moreover, there is the possibility ofundesirable physiological effects from such residual or stored energy onthe users of the fabrics. Such untoward effects would be most likely tooccur in areas where the fabric directly contacts the skin of the weareror user of artifacts made from irradiated materials.

This invention provides a process for the removal of residual energyfrom irradiated cellulosic textile materials.

Briefly, the process of this invention comprises treating a cellulosictextile material, Which material has been subjected to ionizingradiation, in an alkaline bath containing an alkali-metal hydroxide atstrengths above those normally used for mercerization.

It has been found that While the usual mercerization with a lye haslittle or no effect in the removal of the excess or residual radiationenergy, surprisingly when the concentration of the lye is increased suchresidual energy is removed from the textile material. The process ofthis invention can be utilized in conjunction with crosslinking orgrafting reactions of the material effected by means of ionizingradiation. The process has wide application to cellulosic textilematerials, as the term is used herein, as for example to natural ornative cellulose materials such as cotton and to regenerated cellulosematerials such as viscose rayon or cupramrnonium rayon.

The process of this invention and its application to the treatment ofcellulosic materials can be more readily understood by reference toFIGURES l and 2 which are graphic presentations of the results oftreating irradiated cellulosic textile materials with sodium hydroxidesolutions and FIGURES 3 and 4 which are graphic representations ofaction of potassium hydroxide solutions on irradiated cellulosic textilematerials.

The process of this invention is carried out with a solution ofalkali-metal hydroxide stronger than those generally used formercerization. For reasons of convenience and economy, it is generallypreferred to use sodium hydroxide or potassium hydroxide, althoughmixtures of these or other alkali-metal hydroxides can also be used.Preferably, natural or native cellulose is treated in a bath containingalkali-metal hydroxide at a normality of from about 4 to about 9. Thiscorresponds to a sodium hydroxide concentration of from about 14 toabout 34 B. or potassium hydroxide concentrations of from about 22 toabout 39 B. Regenerated cellulose materials are preferably treated inbaths containing from about .2.5 to about 5 N alkali-metal hydroxide,this corresponding to a sodium hydroxide strength of from about 13 toabout 23 B. or a potassium hydroxide strength of from about 15 to about26 B.

The time of treatment required to remove the residual energy can bevaried over wide limits. It is generally preferred that the treatment becarried out for from about 5 to about 20 minutes, the optimum time oftreatment being interrelated with the temperature of treatment as morefully discussed hereinafter.

It is preferred that where the cellulosic textile materialpredominaantly contains natural cellulose it be treated in a bathcontaining from about 8 to about 8.5 N alkali-metal hydroxide at atemperature on the order of C. for from about 5 to about 10 minutes.Similarly, when the cellulosic textile material contains regeneratedcellulose it is preferred to treat it with a 3.5 N

3 (17 B.) sodium hydroxide at from about 15 to about 25 C. for fromabout to about minutes.

The mutual interrelationship of hydroxide concentration and temperatureof treatment for sodium hydroxide and potassium hydroxide used can bereadily appreciated from the graphical representations presented in FIG-URES 1 through 4. The data presented on these graphs represents theresults of treating an imitation cotton poplin fabric which had beensubjected to Co gamma radiation for 10 hours. The abscissas representthe deactivation time, that is, the time of treatment in the alkalimetalhydroxide, and the ordinates represent a measure of the residual energyremaining in the textile material. The amount of residual energy isshown as the magnitude or height of signal obtained from anelectron-spin resonance (ESR) determination on the fabric.

Such means of ascertaining the residual energy left after irradiation ofthe textile material and any subsequent cross-linking or graftingoperation depends upon the fact that an unpaired electron has adetectable magnetic moment. It has been found that this magnetic momentdue to the so-called spin of the unpaired electron provides a measure ofthe residual energy remaining in the material after irradiation andsubsequent operations. As is well-known to those skilled in the art theESR can be determined by a number of methods, one of the most sensitiveand most accurate being the determination of the microwave bandabsorption spectrum of the material under an applied magnetic field. Thedetails of such methods are discussed at length in reference works suchas D. J. E. Ingram, Free Radicals as Studied by Electron Spin Resonance,New York, Academic Press, 1958.

FIGURE 1 illustrates the removal of residual energy from the aforesaidcotton cellulosic textile material when it is treated at 60 C. withsodium hydroxide. This shows that with 8 N (31 B.) sodium hydroxide theresidual radiation energy is completely eliminated after a 10- minuteperiod. When 6 N (26 B.) sodium hydroxide is used, a substantialdiminution of residual energy is obtained after 60 minutes of treatment.Similarly, FIG- URE 2 shows the results obtained with 6 and 8 N sodiumhydroxide at room temperature of to C. In this case, once again the 8 Nsodium hydroxide has completely removed all residual radiation energyafter 10 minutes.

In the same manner, FIGURES 3 and 4 show the results obtained when thetreatment of this invention is carried out with potassium hydroxide at8.5 (37 B.), 7 N (32 B.), and 5.5 N (27 B.) at the indicatedtemperatures. When the treatment is conducted at 60 C. a 8.5 N potassiumhydroxide solution removes all residual radiation energy after 10minutes. In FIGURE 4 where a room temperature of l522 C. is used,residual energy is completely eliminated from the cellulosic textilematerial after a 120-minute treatment with 8.5 N potassium hydroxide.

The following examples are set out to illustrate specific embodiments ofthis invention, and are not indicative of the entire scope of suchinvention, the scope being determined by the claims appended hereto.

EXAMPLE I An imitation cotton poplin fabric having a moisture content of5% (in other words the moisture content in equilibrium with the ambientroom air) was irradiated with gamma rays from a C0 source for 10 hoursto obtain a total dose of 2.2 10 rad. Subsequent to this irradiation thecellulose textile material was tested and found to have a relative ESRsignal magnitude of 130 units.

Subsequently the textile material was treated for 10 minutes in a bathcontaining 8 N sodium hydroxide (about 31 B.) at 15-22 C. A sample wasthen rinsed with water, treated with dilute acetic acid, washed to aEXAMPLE II A viscose rayon having a moisture content of 7% wasirradiated with gamma radiation from a C0 source for 10 hours to producea total dose of 2..2 10 rad. The material was then subjected to an ESRmeasurement which indicated a signal magnitude of 230 units.

The textile was then treated for 10 minutes at 60 with 8.5 N potassiumhydroxide (37 B.). This material was then washed with water and aceticacid and dried as in Example I. When subsequently tested for ESR, nosignal was obtained. Thus, the residual radiation energy was completelyremoved from the viscose rayon by the treatment.

The process of this example is applicable to other regenerated cellulosetextile materials with comparable results.

It will be understood that cross-linking or grafting or other operationscan take place between the irradiation and the elimination of excess orresidual energy by the process of this invention. Further, the otherwell-known alkali-metal hydroxides can be used in this process, although the sodium and potassium hydroxides are preferred because ofavailability and economy.

What is claimed is:

1. A process for removing excess energy which comprises subjecting acellulosic textile material selected from the group consisting of nativecellulose and regenerated cellulose to ionizing radiation in an amountnot greater than about 10 rad and treating the irradiated textilematerial for from about five to about twenty minutes in an aqueousalkaline bath containing from about 4 to about 9 N alkali-metalhydroxide when said material is native cellulose and from about 2.5 toabout 5 N alkalimetal hydroxide when said material is regeneratedcellulose.

2. The process of claim 1 wherein the alkaline bath is at a temperaturein the range of from about 10 to about 30 C.

3. The process of claim 1 wherein the alkaline bath is at a temperaturein the range of from about 50 to about C.

4. A process for removing excess energy which comprises a subjecting atextile material containing natural cellulose to an amount of ionizingradiation not greater than about 10" rad to introduce residual energyinto said material and subsequently treating said material in a bath atabout 60 C. for from about 5 to about 10 minutes, said bath containingfrom about 8 to about 8.5 N alkali-metal hydroxide.

5. The process of claim 4 wherein the alkali-metal hydroxide is sodiumhydroxide.

6. A process for removing excess energy from a textile material whichcomprises subjecting a textile material containing regenerated celluloseto an amount of ionizing radiation not greater than 10 rad andsubsequently treating said material in a bath at a temperature of fromabout 15 to about 25 C. for from about 5 to about 10 minutes, said bathcontaining about 3.5 N alkali metal hydroxide.

7. The process of claim 6 wherein the alkali-metal hydroxide is sodiumhydroxide.

8. A process for removing excess energy which comprises treating acellulosic textile material selected from the group consisting of nativecellulose and regenerated cellulose, said material having been subjectedto ionizing radiation in an amount not greater than about 10" rad whichintroduced residual energy into said material, in an aqueous alkalinebath containing from about 4 to about 5 6 9 N alkali-metal hydroxidewhen said material is na- OTHER REFERENCES tive cellulose and from about2.5 to about 5 N alkali- E Peters, Textile Chemistry, VOL 11 Elseveirmetal hydroxide when the material is regenerated cellulose, removingsaid material from said bath, and subhshmg New York 1967 sequentlyneutralizing any residual alkalinity in said 5 NORMAN G. TORCHIN PrimaryExaminer material.

J. C. CALLAGHAN, Assistant Examiner References Cited US Cl XR UNITEDSTATES PATENTS 204 160,1 3,206,273 9/1965 Munzel 8116 10 3,108,890 10/193 Beaver 2o4 15o. 1

UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No. 3,502,426 Dated March 24, 1970 Inventor-( H. KRASSIG ET AL It is certifiedthat error appears in the above-identified patent and that said LettersPatent are hereby corrected as shown below:

Column 1, lines 5, 6 and 7 delete "to Heberlein Patent Corporation, NewYork, N.Y., a corporation of New York" and insert in lieu thereof bymesne assignments, to Heberlein & Co. A.G. Wattwil, St. Gall,Switzerland, a corporation of Switzerland time are SEALED Attest:

Edward M. Fletcher, Ir. MI E Sam-TYLER, JR Attesting OfficerCommissioner of Patents FORM PO-1050 HO-69l USCOMM-pc 5 g7 -p5g w us.sovllmnlm nmmnc ornct: ll" o-Ju-lu

1. A PROCESS FOR REMOVING EXCESS ENERGY WHICH COMPRISES SUBJECTING ACELLULOSIC TEXTILE MATERIAL SELECTED FROM